It is known, in fact, that the yaw movements of a bogie, consisting of a slow rotation from one side to the other, around its pivot on which the body has been articulated, necessitate considerable braking in a straight line and much less intense braking on a curve, which contradictory requirements have until now not been solved other than by unsatisfactory compromises in the two cases.
As regards a suspension of a vehicle with a large load variation, the braking force, generally proportional to the speed and to the square root of the mass, becomes very unsatisfactory under load if it has been regulated for operation empty, and vice versa.
In another case, which is, for example, that of jacks of machine controls, it is often advantageous to modulate the forward speed of approach and of working by suitable braking, as a function of the various phases of the operation.